// ========================================================================
// Copyright (c) 2004-2009 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
// You may elect to redistribute this code under either of these licenses.
// ========================================================================

package org.eclipse.jetty.continuation;

import java.lang.reflect.Constructor;

import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestWrapper;
import javax.servlet.ServletResponse;

/* ------------------------------------------------------------ */
/**
 * ContinuationSupport. Factory class for accessing Continuation instances, which with either be native to the container (jetty >= 6), a servlet 3.0 or a faux continuation.
 */
@SuppressWarnings("unchecked")
public class ContinuationSupport
{

	static final boolean __jetty6;
	static final boolean __servlet3;
	static final Class<?> __waitingContinuation;
	static final Constructor<? extends Continuation> __newServlet3Continuation;
	static final Constructor<? extends Continuation> __newJetty6Continuation;
	static
	{
		boolean servlet3Support = false;
		Constructor<?> s3cc = null;
		try
		{
			boolean servlet3 = ServletRequest.class.getMethod("startAsync") != null;
			if (servlet3)
			{
				Class<? extends Continuation> s3c = ContinuationSupport.class.getClassLoader().loadClass("org.eclipse.jetty.continuation.Servlet3Continuation").asSubclass(Continuation.class);
				s3cc = s3c.getConstructor(ServletRequest.class);
				servlet3Support = true;
			}
		} catch (Exception e)
		{} finally
		{
			__servlet3 = servlet3Support;
			__newServlet3Continuation = (Constructor<? extends Continuation>)s3cc;
		}

		boolean jetty6Support = false;
		Constructor<?> j6cc = null;
		try
		{
			Class<?> jetty6ContinuationClass = ContinuationSupport.class.getClassLoader().loadClass("org.mortbay.util.ajax.Continuation");
			boolean jetty6 = jetty6ContinuationClass != null;
			if (jetty6)
			{
				Class<? extends Continuation> j6c = ContinuationSupport.class.getClassLoader().loadClass("org.eclipse.jetty.continuation.Jetty6Continuation").asSubclass(Continuation.class);
				j6cc = j6c.getConstructor(ServletRequest.class, jetty6ContinuationClass);
				jetty6Support = true;
			}
		} catch (Exception e)
		{} finally
		{
			__jetty6 = jetty6Support;
			__newJetty6Continuation = (Constructor<? extends Continuation>)j6cc;
		}

		Class<?> waiting = null;
		try
		{
			waiting = ContinuationSupport.class.getClassLoader().loadClass("org.mortbay.util.ajax.WaitingContinuation");
		} catch (Exception e)
		{} finally
		{
			__waitingContinuation = waiting;
		}
	}

	/* ------------------------------------------------------------ */
	/**
	 * Get a Continuation. The type of the Continuation returned may vary depending on the container in which the application is deployed. It may be an implementation native to the container (eg org.eclipse.jetty.server.AsyncContinuation) or one of the utility implementations provided such as an internal <code>FauxContinuation</code> or a real implementation like {@link org.eclipse.jetty.continuation.Servlet3Continuation}.
	 * 
	 * @param request The request
	 * @return a Continuation instance
	 */
	public static Continuation getContinuation(ServletRequest request)
	{
		Continuation continuation = (Continuation)request.getAttribute(Continuation.ATTRIBUTE);
		if (continuation != null)
			return continuation;

		while (request instanceof ServletRequestWrapper)
			request = ((ServletRequestWrapper)request).getRequest();

		if (__servlet3)
		{
			try
			{
				continuation = __newServlet3Continuation.newInstance(request);
				request.setAttribute(Continuation.ATTRIBUTE, continuation);
				return continuation;
			} catch (Exception e)
			{
				throw new RuntimeException(e);
			}
		}

		if (__jetty6)
		{
			Object c = request.getAttribute("org.mortbay.jetty.ajax.Continuation");
			try
			{
				if (c == null || __waitingContinuation == null || __waitingContinuation.isInstance(c))
					continuation = new FauxContinuation(request);
				else
					continuation = __newJetty6Continuation.newInstance(request, c);
				request.setAttribute(Continuation.ATTRIBUTE, continuation);
				return continuation;
			} catch (Exception e)
			{
				throw new RuntimeException(e);
			}
		}

		throw new IllegalStateException("!(Jetty || Servlet 3.0 || ContinuationFilter)");
	}

	/* ------------------------------------------------------------ */
	/**
	 * @param request the servlet request
	 * @param response the servlet response
	 * @deprecated use {@link #getContinuation(ServletRequest)}
	 * @return the continuation
	 */
	@Deprecated
	public static Continuation getContinuation(final ServletRequest request, final ServletResponse response)
	{
		return getContinuation(request);
	}
}
